| Abstract
| - Amphiphilic bowl-shaped receptor molecules have been synthesized starting from diphenylglycoluril.Upon dispersion in water, these molecules self-assemble to form vesicles that bind neutral guestsand alkali metal ions. In the case of bis(alkylester)-modified receptor compound 4, electronmicroscopy reveals that an increase in the size of the alkali metal ion (from Na+ or K+ to Rb+ andto Cs+) leads to a change in the shape of the aggregates, viz. from vesicles to tubules. Monolayerexperiments suggest that this behavior is due to a change in the conformation of this amphiphilicreceptor. In water, molecules of 4 have an elongated conformation that changes to a sandwich-likeone upon binding of alkali metal ions. Binding studies with vesicles from the bis-ammoniumreceptors 6 and 9 and the guest 4-(4-nitrophenylazo)resorcinol (Magneson) reveal that below thecritical aggregation concentration (CAC) of the amphiphile 1:1 host−guest complexes are formedwith high host−guest association constants. Above the CAC, a host−guest ratio of 2:1 was observedthat indicates that only the cavities on the outside of the vesicle can be occupied. In the case of thenaphthalene walled compound 8 changes in the vesicle structure are induced by the organic guestMagneson.
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